Photographic medium



Patented Feb. 23, 1926.

- UNITED STATES PATENT OFFICE.

I MURRAY 0. BEEBE AND ALEXANDER MURRAY, OF CINCINNATT, OHIO, ASSIGNORS TO THE WADSWORTH WATCH CASE COMPANY, OF DAYTON, KENTUCKY, CORPORA- PHOTOGRAPHIC MEDIUM.

No Drawing. Application filed November To all whom it may concern:

Be it known that We, (a) MURRAY G.

BEEBE and b) ALEXANDER MURRAY, (MUR- RAY C. BEEBE is a citizen of the United nexed claims.

The purpose of our invention is to provide a non-aqueous photographic medium that is stable and not liable to deterioration during storage; that contains an emulsoid base such as oleaginous materials perma- I nently sensitized 1n a non-aqueous medium;

that through the cooperation of the colloidal characteristics of the sensitizer. and a single developer produces brilliant results; that overcomes the difliculty of clearing the high lights encountered in the use of oleaginous coatings with non-colloidal sensitizers; and that provides a. photographic medium, in which a change from the sol to the gel state is effected by light through the cooperation of a colloidal suspension of a metal halide,

combined therewith as a sensitizen With these and other ends inview, we herewith set forth such expediehts' as will be exemplifications or instances of adaptation of the broad underlying features of our invention Without limiting ourselves to the specific details described herein.

The following description of procedure in practically applying our invention is exemplary and not a limiting disclosure, as variations in degree and within the range of practical equivalents may be made without departing from the spirit of our invention. Among numerous other oleaginous mediums we may use glycerides of unsaturated fatty acids such as tun oil, perilla oil etc, combined with. metalllc resinates and" a colloidal sensitizer' approximately as follows or in hoto- 18, 1922. Serial No. 601,884.

practical variations therefrom. The proportions given are by weight Oleagz'nods mediwm.

\ Per cent. Tiing oil 7. 50 Perilla oil 1. 91

Gollaidal sensz'tz'eer.

. Per cent. Lead. resinate 0. 67 Iodoform 5. Lead triethyl iodide 7. 00

I Sol vents.

. Per cent. Ketones 27.00 Benzene 45. 5O Solvent naphtha 5. 42

The combined sensitizer and coating medium may be made as follows: A solution of 4.2 grams of lead triethyl iodidecontained in approx'mately 30 cc. benzene is combined with grams of the oleaginous medium, to which is added 3 grams of iodoform-dissolved in cc. of ethyl methyl ketone. The

lead 'resinate may be mixed with the benzol (benzene) and lead triethyl iodide, and the solvent naphtha may be added as a thinner for thevarnish which comprises the other substances.

The coating medium with its incorporated sensitizer, soon after mixing, changes to a canary-yellow color whenobserved by reflected light, and an orange red when inspected by transmitted light, having, in

either case, an opalescent appearance. This color is likel due to the formation of an iodide of lea which is in a suspensoid state known as an organosol because an organic dispersing medium is used. Small amounts of water-or any aqueous reagents cause a rapid deterioration through the formation of a non-colloidal suspension which roduoes an unstable medium thatWill rapidly decrease its sensitivity.

y In preparing the resist or coating in about the manner described we secure a reasonably permanent photo-sensitive menstruum which can be kept in brown bottles, in the dark for days and weeks in contrast to sensitizers which are non-colloidal. To secure the required sensitivity it is not necessary to form the lead iodide; but by allowing the salt, if formed, to remain in a colloidal state it plays an important cooperating function of sensitization by avoiding rapid deterioration which would inevitably take place if the lead salt was allowed to precipitate. By reason of these safeguards our non-aqueous photographic medium has many practical advantages over our prior procedures in this art.

Another important feature lies in the property of the sensitizer to not deleteriously affect the oil colloids during storage of the medium. Since no catalytic drier like cobalt linoleate etc., is used, a metallic or other suitable plate can be coated and kept for many hours without drying or becoming set. When a plate with such a coating is exposed to a luminous image, the parts which are subjected to the greatest illumination gel very rapidly, and become comparatively insoluble and non-'detergiable producing a result of maximum contrast, even when a low luminous intensity is used; for instance in making great enlargements from small sized half-tone negatives by optical projection for poster work. I

The plates are coated by flowing the medium overthem or applying it otherwise and are then set on edge to drain and also permit the solvents to evaporate. Our present medium is more highly sensitive than when only free iodine is .used as a sensitizer. In proof of this we may state that We have optically enlarged a 4. x 5- half tone negative to 32 x 42 on a grained zinc platein ten minutes under the illumination usually produced by are printing lamps found in process engraving establishments. In contrastto this result when medium are sensitized with free iodine the ex sure was 16 minutes under. the same con 'tions and natures.

with water securing a clear print which retained all the sharpness of the half-tone dots, without the presence of scum between them. When working same size the exposure time is approximately 10 seconds under a similar source of luminosity.

Our process is specially adaptable for the production of poster enlargements by direct or off-set lithography. Heretofore the difiiculties have been, lack of permanency of the prepared medium, disturbing side reactions causing a combination of the free halogen with the oil, and an oxidation reaction which made it impossible to coat lates by 'fiowing or to preserve coated p ates for some time. There has existed a limitation in the use of developers which resulted in a lack of sharp detail. luminosity we now avoid this and secure a Under the same degree of brilliancy, speed and accuracy that has not been attainable hitherto.

By eliminating the side action we secure uniform conditions as to exposure which under other procedures has been variable and uncertain.

What we claim is:

1. A photographic medium comprising a .hydrophobic colloid and a sensitizer comprising lead triethyl iodide.

2. A photographic medium comprising a hydrophobic colloid and a sensitizer comi ,prising lead triethyl iodide and a halogenliberating organic compound.

3. A photographic medium comprising a h drophobic colloid and sensitizing means dispersed therein comprising lead triethyl iodide and iodoform.

4. A photographic medium comprising a hydrophobic colloid and sensitizing means dispersed therein comprising lead triethyl iodide, iodoform, and a resinate.

5. A photographic medium comprising a light-sensitive oi and a sensitizer comprising lead triethyl iodide and iodoform.

In testimony whereof we afiix our sig MURRAY 0. BEEBE. ALEXANDER MURRAY. 

